Reactor protection systems require periodic testing. Testing of reactor protection systems requires the exchange of status information between independent channels of plant protection systems (xe2x80x9cPPS""sxe2x80x9d) and trains of engineered safety features (xe2x80x9cESF""sxe2x80x9d). Digital implementation of these systems introduces the inherent problem of maintaining channel/train independence while sustaining communications integrity and function. Typical fiber optic communication networks provide the required electrical isolation and independence between channels and trains. However, they do not address the failure modes associated with them.
Directed to achieving the foregoing and additional objectives and overcoming shortcomings of the prior art systems, a main object of the invention is to provide an optical communications network that provides a means for exchanging required information between redundant PPS channels and ESF trains.
A further object of the invention is to provide an optical communications network that provides required electrical isolation, fault tolerance addressing credible single failures which include loss of AC power from a single vital bus power source.
Still, a further object of the invention is to provide an optical communications network that employs a unique configuration of fiber optic cables, fiber optic modems, and power assignment to sustain the communications between independent and redundant PPS channels and independent and redundant ESF trains.
The above objectives and others are provided by a communication network for a nuclear power PPS, which includes a plurality of monitoring and control channels, including a first pair of channels which has a first and second channel, the first pair of channels directly communicating through a network of fiber optic data paths with a second pair of channels which has a third channel and a fourth channel; a plurality of engineered safety feature trains, including a first train and a second train, the first train communicating directly with the first pair of channels, and communicating directly with the second train, the second train communicating directly with the second pair of channels, and communicating directly with said first train; a first vital power bus, individually powering the first channel; a second vital power bus, individually powering the second channel, and redundantly powering the first train together with the first vital power bus; a third vital power bus, individually powering the third channel; and a fourth vital power bus, individually powering the fourth channel, and redundantly powering the second train together with the third vital power bus.
The communications network further includes a first plurality of fiber optic modems associated with each of the monitoring and control channels; and a second plurality of modems associated with each of the engineered safety trains. The first vital power bus individually powers a first group of modems, the second vital power bus individually powers a second group of modems, the third power bus individually powers a third group of modems, and the fourth vital power bus individually powers a fourth group of modems, the first, second, third and fourth groups of modems being part of the first plurality of modems.
Also, the first vital power bus redundantly powers a fifth group of modems, together with the second vital power bus, the fifth group of modems being part of said second plurality of modems; and the third vital power bus redundantly powers a sixth group of modems, together with the fourth vital power bus, the sixth group of modems being part of the second plurality of modems.
The above objects and others are also accomplished by a method of monitoring and controlling a nuclear power plant protection system, which includes the steps of providing a plurality of monitoring and control channels, including a first pair of channels which has a first and second channel, the first pair of channels directly communicating through a network of fiber optic data paths with a second pair of channels which has a third channel and a fourth channel; providing a plurality of engineered safety feature trains, including a first train and a second train, the first train communicating directly with the first pair of channels, and communicating directly with the second train, the second train communicating directly with the second pair of channels, and communicating directly with the first train, the communication occurring through the network of data paths; individually and separately powering the first, second, third, and fourth channels using a first, second, third, and fourth vital power bus, respectively; redundantly powering the first train using the first and second vital power buses; and redundantly powering the second train using the third and fourth vital power buses.
The method further includes the steps of providing a first plurality of fiber optic modems associated with each of the monitoring and control channels; and providing a second plurality of fiber optic modems associated with each of the engineered safety feature trains. The method also includes the steps of individually powering a first, second, third, and fourth group of modems using the first, second, third, and fourth vital power buses respectively, the first, second, third and fourth groups of modems being part of the first plurality of modems. The method may also include the steps of redundantly powering a fifth group of modems using the first and second vital power buses, the fifth group of modems being part of the second plurality of modems; and redundantly powering a sixth group of modems using the third and fourth vital power buses, the sixth group of modems being part of the second plurality of modems.